60Coγ射线辐照对碳纤维表面及其复合材料层间剪切强度的影响

对60Coγ射线辐照处理的PAN 基碳纤维的力学性能、表面形貌及表面结构的变化和其与环氧树脂复合后层间剪切强度进行了初步的研究。60Coγ射线在1×102～ 1×103Gy 辐照剂量时, 使PAN 基中强碳纤维本身的力学性能显著提高; 使碳纤维表面的含氧官能团浓度和石墨化程度得以提高; 由此制备的碳纤维环氧复合材料的层间剪切强度SIL SS提高了31% 左右。而在辐照剂量≥1×104Gy 时, 由于辐照损伤及热效应, 使碳纤维的力学性能下降, 增加了表面的炭化及其撕裂程度,从而减小了碳纤维环氧复合材料的层间剪切强度SIL SS。     

Synthesis of niobium oxide nanowires using an atmospheric pressure plasma jet

A rapid synthesis of niobium oxide nanowires using an oxygen atmospheric pressure plasma jet sustained by repetitive DC pulse power is presented. Using this plasma jet to treat niobium foils, niobium oxide nanowires (NWs) with the length up to 3-6 μm and the diameter of 100-200 nm can be fabricated within 20 s. Parametric studies show that a high growth rate can be obtained with the synergetic effect of the temperature and the reactivity of the plasma jet. The structural analysis of the jet treated niobium foil shows that in the case that no NW is formed, the major phases are Nb₆O and orthorhombic Nb₂O₅ while with the presence of NWs, high crystalline monoclinic Nb₂O₅ is the dominant phase.     

Functionalization of carbon nanotubes by water plasma

Multiwall carbon nanotubes grown by plasma enhanced chemical vapour deposition were functionalized by H(2)O plasma treatment. Through a controlled functionalization process of the carbon nanotubes (CNTs) we were able to modify and tune their chemical reactivity, expanding the range of potential applications in the field of energy and environment. In particular, different oxygen groups were attached to the surfaces of the nanotubes (e.g. carboxyl, hydroxyl and carbonyl), which changed their physicochemical properties. In order to optimize the main operational parameters of the H(2)O plasma treatment, pressure and power, a Box-Wilson experimental design was adopted. Analysis of the morphology, electrochemical properties and functional groups attached to the surfaces of the CNTs allowed us to determine which treatment conditions were suitable for different applications. After water plasma treatment the specific capacitance of the nanotubes increased from 23?up to 68?F?g(-1) at a scan rate of 10?mV?s(-1).     

Nonvolatile memory effect of tungsten nanocrystals under oxygen plasma treatments

In this work, an oxygen plasma treatment was used to improve the memory effect of nonvolatile W nanocrystal memory, including memory window, retention and endurance. To investigate the role of the oxygen plasma treatment in charge storage characteristics, the X-ray photon-emission spectra (XPS) were performed to analyze the variation of chemical composition for W nanocrystal embedded oxide both with and without the oxygen plasma treatment. In addition, the transmission electron microscopy (TEM) analyses were also used to identify the microstructure in the thin film and the size and density of W nanocrystals. The device with the oxygen plasma treatment shows a significant improvement of charge storage effect, because the oxygen plasma treatment enhanced the quality of silicon oxide surrounding the W nanocrystals. Therefore, the data retention and endurance characteristics were also improved by the passivation.     

Non-thermal plasma for oxidation of gaseous products originating from thermal treatment of wastes

A plasma reactor generating non-equilibrium plasma in a gliding discharge was applied as one of the modules of a new laboratory device for hazardous waste destruction. The degradation process of wastes containing an organic part was carried out in two stages. The first one consisted of thermal decomposition of wastes in an inert atmosphere (pyrolysis process in argon flow—the gaseous products are formed from the organic part of wastes). In the second stage products of pyrolysis were oxidized in a gliding discharge. This work was focused on study of the parameters influencing the oxidation process of gases originating from pyrolysis and flowing into the plasma reactor. Oxygen was introduced into the plasma reactor simultaneously with the gases. We investigated two factors significantly affecting the oxidation process: (a) the oxygen concentration in the initial mixture of argon and oxygen and (b) the total flow of argon and oxygen gases. The best oxidation efficiency of the processing gases in the plasma was reached when the oxygen content did not exceed 20% and when the total flow of argon and oxygen was low enough not to cause disturbances of functioning of the plasma reactor.     

Thickness dependent reactivity and coercivity for ultrathin Co/Si(111) films

For Co/Si(111) films thinner than 15 ML, the thickness dependent reactivity and magnetic properties have been systematically studied. As the Co coverage increases, Co adatoms on the Si(111) surface show enhanced chemical reactivity for oxidation due to the change of the chemical state. After the saturation oxygen exposure, oxygen atoms interact with a thick Co layer to form a rougher interface. Complex adsorption kinetics of oxygen in the Co layer is observed. From the depth-profiling measurements for Co layers close to the Co-Si interface, the sputtering rate is enhanced due to that the solid surfaces of Si and Co-Si compounds are resistive against oxidation. The descending of the Kerr intensity by saturation oxygen exposure shows the limited diffusion length of oxygen atoms into the films. The inertness of the Co-Si interface, the reduction of pure cobalt and imperfection introduced by oxygen influence the coercivity of O/Co/Si(111).     

Oxidation properties of mesophase pitch prepared by a heterogeneous nucleation method

Mesophase pitches prepared by a heterogeneous nucleation method from various mixtures of coal tar-derived isotropic pitch and petroleum-derived mesophase pitch (MP-P) were oxidatively stabilized, and the dependence of chemical reactivity and stabilization rate on their chemical structure was investigated. The rate and amount of oxygen uptake of the mesophase pitch fibres, revealed by thermogravimetry, increased under given conditions of oxidation with the amount of added MP-P, but the rate of stabilization showed a reverse trend. The lower chemical reactivity of coal tar-derived mesophase pitch (MP-C) appears to induce a slower rate of oxygen uptake, while the higher content of pyridine-insoluble fraction and higher aromaticity of MP-C may result in a lesser content of oxygen being required for stabilization, as compared with MP-P.     

Electrosynthesis of Hydrogen Peroxide Synergistically Catalyzed by Atomic Co–Nx–C Sites and Oxygen Functional Groups in Noble‐Metal‐Free Electrocatalysts

Hydrogen peroxide (H₂O₂) is a green oxidizer widely involved in a vast number of chemical reactions. Electrochemical reduction of oxygen to H₂O₂ constitutes an environmentally friendly synthetic route. However, the oxygen reduction reaction (ORR) is kinetically sluggish and undesired water serves as the main product on most electrocatalysts. Therefore, electrocatalysts with high reactivity and selectivity are highly required for H₂O₂ electrosynthesis. In this work, a synergistic strategy is proposed for the preparation of H₂O₂ electrocatalysts with high ORR reactivity and high H₂O₂ selectivity. A Co?N_x?C site and oxygen functional group comodified carbon‐based electrocatalyst (named as Co–POC–O) is synthesized. The Co–POC–O electrocatalyst exhibits excellent catalytic performance for H₂O₂ electrosynthesis in O₂‐saturated 0.10 m KOH with a high selectivity over 80% as well as very high reactivity with an ORR potential at 1 mA cm^?2 of 0.79 V versus the reversible hydrogen electrode (RHE). Further mechanism study identifies that the Co?N_x?C sites and oxygen functional groups contribute to the reactivity and selectivity for H₂O₂ electrogeneration, respectively. This work affords not only an emerging strategy to design H₂O₂ electrosynthesis catalysts with remarkable performance, but also the principles of rational combination of multiple active sites for green and sustainable synthesis of chemicals through electrochemical processes.     

Effect of oxygen injection on synthesizing barium titanate nanoparticles by plasma chemical vapor deposition

Nanoparticles of barium titanate were prepared by plasma chemical vapor deposition using an inductively coupled plasma technique that has a high potential for preparing nanoparticles. The present paper describes the details of the reaction control achieved by accelerating the reactions between Ba atoms and oxygen using direct injection of oxygen into the tail of the plasma flame. According to our previous reports, the crystalline phases of the powder products were different at each collection area in the CVD apparatus. This was due to the remaining active Ba atoms without a reaction in the plasma tail flame, as observed from the optical emission spectroscopy. After the reactions between Ba atoms and oxygen occurred by direct oxygen injection, BaTiO₃ perovskite phases were produced as a major phase in each collection area. The optimal oxygen injecting conditions for obtaining perovskite BaTiO₃ single phase are summarized as follows: the temperature of the plasma tail flame at oxygen-injecting position = approximately 1000 K and molar ratio of oxygen to the reactants (O₂/(Ba+Ti)) = 4000. Furthermore, BaTiO₃ nanoparticles with average particle size under 10 nm were prepared by oxygen injection (the average particle size without oxygen injection is 15.4 nm). Well-crystallized BaTiO₃ nanoparticles with spherical shape were observed by TEM.     

Controlled surface modification of boron nitride nanotubes

Controlled surface modification of boron nitride nanotubes has been achieved by gentle plasma treatment. Firstly, it was shown that an amorphous surface layer found on the outside of the nanotubes can be removed without damaging the nanotube structure. Secondly, it was shown that an oxygen plasma creates nitrogen vacancies that then allow oxygen atoms to be successfully substituted onto the surface of BNNTs. The percentage of oxygen atoms can be controlled by changing the input plasma energy and by the Ar plasma pre-treatment time. Finally, it has been demonstrated that nitrogen functional groups can be introduced onto the surface of BNNTs using an N(2) + H(2) plasma. The N(2) + H(2) plasma also created nitrogen vacancies, some of which led to surface functionalization while some underwent oxygen healing.     

Improved proliferation of human osteosarcoma cells on oxygen plasma treated polystyrene

Polystyrene (PS) foils were exposed to oxygen plasma in order to improve the ability of human osteosarcoma cells (HOS) proliferation. Plasma was created in an electrodeless radio-frequency (RF) discharge in pure oxygen. Plasma treatment time of 30 s allowed for saturation of the surface with oxygen rich functional groups. Incubation of proteins from cell culture media was studied versus incubation time for untreated and plasma treated PS by X-ray photoelectron spectroscopy (XPS). Then HOS cells were cultivated according to a standard procedure, applied on the PS substrates and incubated. The proliferation was studied qualitatively by optical microscopy, scanning electron microscopy (SEM) and quantitatively by MTT assay. All techniques revealed significant differences in HOS cells proliferation on untreated and oxygen plasma treated PS. The differences were most pronounced after 24 h of incubation when the cells have already stared to proliferate on plasma treated PS, while they were still in quiescence on untreated PS. The confluency was achieved till the 6th day on plasma treated PS, while on untreated PS such confluency has never been achieved. The cell viability assay revealed that HOS cells grew better on plasma treated PS for various incubation times. Similar trend was observed regarding the adhesion of proteins. They adhered better on plasma treated PS causing better environment for further cell proliferation. The results clearly show that oxygen plasma treatment allows for much better proliferation of HOS cells on plasma treated PS as compared to the untreated PS substrates.     

Effect of target oxidation on reactive sputtering rates of titanium in argon-oxygen plasmas

Reactive sputtering rates of titanium in argon-oxygen plasmas were studied as a function of oxygen and argon partial pressures in an r.f. diode sputtering system at 2 keV bias voltage. The sputtering rate changed by an order of magnitude at a critical oxygen mole fraction in the plasma equal to 0.0070. This transition corresponds to the onset of target oxidation. The threshold for target oxidation is shown to be independent of the total plasma pressure, and to be specified uniquely by a critical mole fraction of oxidant in the plasma.     

Characterization of an Ar/O2 magnetron sputtering plasma using a Langmuir probe and an energy resolved mass spectrometer

An argon plasma with a small amount of oxygen in a radio-frequency magnetron sputtering system has been studied experimentally. A Langmuir probe has been used to measure the ion density, electron temperature and plasma potential in the plasma, whereas an energy-resolved mass spectrometer has been used to investigate the ions flowing towards the growing film. It has been found that the argon ion density decreases when the oxygen gas is added to the plasma above a certain flow. A discussion on which process is responsible for this effect is presented.     

New Insight into the Development of Oxygen Carrier Materials for Chemical Looping Systems

Chemical looping combustion (CLC) and chemical looping reforming (CLR) are innovative technologies for clean and efficient hydrocarbon conversion into power, fuels, and chemicals through cyclic redox reactions. Metal oxide materials play an essential role in the chemical looping redox processes. During reduction, the oxygen carriers donate the required amount of oxygen ions for hydrocarbon conversion and product synthesis. In the oxidation step, the depleted metal oxide oxygen carriers are replenished with molecular oxygen from the air while heat is released. In recent years, there have been significant advances in oxygen carrier materials for various chemical looping applications. Among these metal oxide materials, iron-based oxygen carriers are attractive due to their high oxygen-carrying capacity, cost benefits, and versatility in applications for chemical looping reactions. Their reactivity can also be enhanced via structural design and modification. This review discusses recent advances in the development of oxygen carrier materials and the mechanisms of hydrocarbon conversion over these materials. These advances will facilitate the development of oxygen carrier materials for more efficient chemical looping technology applications.     

Oxygen plasma etching of silver-incorporated diamond-like carbon films

Diamond-like carbon (DLC) film as a solid lubricant coating represents an important area of investigation related to space devices. The environment for such devices involves high vacuum and high concentration of atomic oxygen. The purpose of this paper is to study the behavior of silver-incorporated DLC thin films against oxygen plasma etching. Silver nanoparticles were produced through an electrochemical process and incorporated into DLC bulk during the deposition process using plasma enhanced chemical vapor deposition technique. The presence of silver does not affect significantly DLC quality and reduces by more than 50% the oxygen plasma etching. Our results demonstrated that silver nanoparticles protect DLC films against etching process, which may increase their lifetime in low earth orbit environment.     

Plasmamessungen und Schichteigenschaften

Plasma Analysis and Thin Film Properties of Sputter‐ and Ionplating PVD‐Processes For a large number of thin film applications just few thin film coating processes are used in industrial scale production. For example, Magnetron Sputtering (MS), Ionplating (IP), Arc Source Ablation (AS) and technical variations of them. Recent developments allow beside traditional dc modes also the use of pulsed dc modes, as for instance in magnetron sputtering and arc source deposition. In this work the Reactive Low Voltage Ionplating (RLVIP) with pulsed substrate bias (Ionplating Plasma Assisted IPPA), DC and DC‐pulse Magnetron Sputtering and Arc source deposition in DC‐ and DC‐pulse mode is of interest concerning their plasma. Pulsing the substrate‐bias of the RLVIP (IPPA) influences film stress and optical absorption but is not easy to handle in industrial production. Pulsing the sputter processes leads to massive changes in the coating plasma and the coatings itself. And finally pulsing the arc‐current of the Arc Source Ablation processes implements advantages for lower cathode temperatures, for use of less conducting cathode materials, less droplet formation and improved chemical reactivity with oxygen.     

Estimating the electrochemical reactivity of pyrite ores-their impact on pulp chemistry and chalcopyrite flotation behaviour

Prudent control of ore pulp chemistry via parameters such as redox potential (Eh), dissolved oxygen (DO) and pH, can markedly improve the flotation recovery, grade and selectivity of sulphide minerals. In this paper, the electrochemical reactivities of two pyrite minerals and their impact on chalcopyrite flotation are investigated using oxygen demand test and froth flotation. Changes in the surface chemistry/speciation are also investigated using X-ray photoelectron spectroscopy (XPS) and EDTA extraction technique. The oxygen demand test shows that the different pyrite ores display significantly different electrochemical reactivity. Furthermore, continuous aeration of the pulp reduces the reactivity of the pyrite ores. Solution and surface analysis results suggest the formation of hydroxide surface coatings on the pyrite surface as aeration progresses, preventing or minimising further oxidative reactions from taking place in the pulp. Flotation results showed that the flotation response of chalcopyrite is influenced by the pulp DO/Eh, and therefore the type and reactivity of the pyrite associated with it.     

Oxidation of vanadium with reactive oxygen plasma: A photoelectron spectroscopy study of the initial stages of the oxide growth process

We report on the oxidation of vanadium surface in a low-temperature oxygen plasma studied by in-situ photoelectron spectroscopy (XPS, UPS). Pure vanadium foil was exposed to the oxygen plasma for different time intervals allowing to investigate early stages of the oxide-metal interface formation process and the oxide film growth. Upon increasing the exposure time to the oxygen plasma we identify two regimes with respect to the vanadium oxidation state: formation of 4+ state on the early stages of growth and in saturated regime vanadium was found to be predominantly in the 5+ oxidation state. Angle-resolved XPS was used to perform an in-depth distribution analysis of chemical composition in outermost layers of the oxide. We found that plasma oxidation produces a well-pronounced interface with a transition layer thickness of about 1.3 nm.     

Various microplasma jets and their sterilization of microbes

Various microplasma jets including coplanar-electrodes device, hollow-electrode device, twin injection-needle device, jet from a flexible tube, and pencil-type electrode will be discussed. Argon plasma jets penetrate deep into ambient air and create a path for oxygen radicals to sterilize microbes including spores. A sterilization experiment with bacterial endospores indicates that an argon-oxygen plasma jet very effectively kills endospores of Bacillus atrophaeus (ATCC 9372), thereby demonstrating its capability to clean surfaces and its usefulness for reinstating contaminated equipment as free from toxic biological agents. The key element of the sterilization is the oxygen radicals. The pencil-type configuration produces a long cold plasma jet capable of reaching 3.5 cm and having various excited plasma species shown through optical emission spectrum. By introducing an appropriate gas flow rate, striated discharge patterns in the plasma jet from the pencil-type configuration are produced through ionization wave propagation. 2 W operation of an air plasma jet in pencil-type electrode provides an excellent opportunity for sterilization of microbes. Finally, the twin plasma columns in the twin injection-needle device will be introduced.     

Evaluation of the reactivity of titanium with mould materials during casting

A methodology for evaluating the reactivity of titanium with mould materials during casting has been developed. Microhardness profiles and analysis of oxygen contamination have provided an index for evaluation of the reactivity of titanium. Microhardness profile delineates two distinct regions, one of which is characterised by a low value of hardness which is invariant with distance. The reaction products are uniformly distributed in the metal in this region. The second is characterised by a sharp decrease in microhardness with distance from the metal-mould interface. It represents a diffusion zone for solutes that dissolve into titanium from the mould. The qualitative profiles for contaminants determined by scanning electron probe microanalyser and secondary ion mass spectroscopy in the as-cast titanium were found to be similar to that of microhardness, implying that microhardness can be considered as an index of the contamination resulting from metal-mould reaction.